Introduction

Research
background

(Tove A. Larsen, Judit Lienert)

Urine
source separation is based on a simple insight: most of the nutrients in wastewater
– about 80% of the nitrogen and 50% of the phosphorus – derive from urine,
which itself accounts for less than 1% of the total volume of wastewater. In
the twentieth century, wastewater treatment plants in Europe were expanded specifically
to deal with these nutrients, as they produced toxic effects (e.g. ammonium in rivers)
or excessive algal growth (e.g. phosphorus in lakes). At treatment plants,
major efforts were undertaken to precipitate phosphorus, to convert ammonium to
nitrate and to then eliminate the latter.

The "NoMix
technology" concept is also simple: urine is collected in the front compartment
of specially designed toilets and drained, with a little flushing water or even
undiluted, into a local storage tank. The back compartment of these toilets
operates on the same principle as conventional models; the waste matter collected
is flushed into the sewers with water. One of the Novaquatis research topics
was how urine is to be subsequently managed: the nutrients nitrogen and phosphorus
are used to produce a fertilizer – or are removed by processes similar to those
applied at wastewater treatment plants.

Separating
urine from wastewater would offer various advantages: wastewater treatment
plants could again be built on a smaller scale, and at the same time waterbodies
could be more effectively protected from nitrogen and phosphorus inputs. The
nutrients could be recycled to agriculture, and the micropollutants in urine – hormones
and pharmaceutical residues – could be removed without being mixed with wastewater.
Urine source separation would thus clearly increase the flexibility of wastewater
treatment. In the face of global water scarcity, the NoMix technology also represents
an excellent way of improving the quality of reused water.

The
NoMix technology has major potential. However, the costs need to be competitive
with conventional technologies, since problems of water pollution control and phosphorus
recycling to agriculture can often also be addressed using conventional methods.

Beyond
end-of-pipe solutions: There are alternatives to wastewater treatment plants
for pollution control (Photo Abwasserverband Altenrhein)

In
Novaquatis, we studied whether, in what form and in what circumstances the
NoMix technology is a viable option. As a wide range of questions are involved,
the projects were organized into work packages reflecting the stages of a
possible nutrient cycle.

Results
and synthesis

Gratifyingly,
the NoMix technology meets with a high level of approval among the public. All
the people surveyed in Novaquatis were familiar with and had used the still-immature
technology. Although they recognized the drawbacks of today’s NoMix toilets, the
overwhelming majority found the basic idea convincing (Nova 1). Practitioners also
show considerable interest: in Canton Basel-Landschaft, for example, large-scale pilot
projects were successfully conducted (Nova PP). With regard to conservation of
resources, the NoMix technology also performs well: it has the potential to
make a major contribution to water pollution control in an energy-efficient
manner. In addition, in areas of nutrient scarcity, urine represents a local nutrient
resource (Nova 7).

The
difficulties are in the detail, and urine transport proved to be the most
problematic point. Installing new pipes or transporting urine by tanker from
basement storage tanks for centralized treatment would be a complex and costly
undertaking. In Novaquatis, we elaborated low-cost solutions for transporting urine
via the existing sewer system (Nova 3). However, despite their potential, they
failed to convince the project partners from the sanitary technology industry. These
approaches are too closely tailored to Swiss conditions and are also only
suitable for relatively small catchment areas. The sanitary industry therefore
considers the market potential to be too low to justify investments in the NoMix
technology (Nova 2). Improved sanitary technology is, however, indispensable; although
pilot projects can be carried out with today's NoMix toilets – larger-scale demonstration
projects are not feasible (Nova PP). The objections raised by the sanitary
industry will thus have a decisive influence on future developments.

At the
same time, literature studies (Nova 7) indicated the huge potential of the
NoMix technology from a global perspective. Coastal waters in particular are
severely threatened by nutrient overload. As a result of explosive population
growth in these regions, the problems associated with nutrients from wastewater
are becoming increasingly prominent on the global agenda. Greater elimination
of nutrients is required – which is at present being carried out almost exclusively
in industrialized countries. In areas currently lacking a fully developed
infrastructure, the NoMix technology can protect water resources more rapidly
and effectively than the expansion of sewers and treatment plants. The potential
of the NoMix technology in cases where acute population pressures give rise to
intractable water pollution control problems was impressively demonstrated by
the example of China (Nova 8).

Ultimately,
the key issues are cost-effectiveness and the technical and organizational
possibilities of urine source separation. If urine could be readily transported,
centralized urine treatment would be the option of choice. Methods already
exist (Nova 4), and processes such as phosphorus precipitation and biological nitrogen
elimination can be applied much more cheaply and energy-efficiently to concentrated
urine than to wastewater. Great potential also attaches to methods for the
recovery of nitrogen and elimination of micropollutants – pharmaceuticals and
hormones excreted by humans and detectable in waterbodies. Urine in wastewater
accounts for an estimated 50% of the ecotoxicological hazard posed by these
substances (Nova 5).

Given the difficulties
and/or cost of transport, the potential and cost-effectiveness of decentralized
processes need to be considered. Urine treatment on site appears to be an
attractive option. However, it was not possible within the Novaquatis project
to study decentralized processes in detail. Here, too, the combination of phosphorus
precipitation and biological nitrogen elimination would certainly be a
promising approach. We are confident that mass production could make decentralized
processes economically attractive for the sanitary and other industries. More
problematic, in our view, is the stability of decentralized technologies and the
level of maintenance required, especially in the case of biological processes. To
facilitate the adoption of the NoMix technology, the two types of solution
could be pursued in parallel. In view of Eawag's scientific expertise, we are
better qualified to develop stable biological processes and solutions for the organizational
problems of decentralized treatment than to identify new options for urine
transport.

Conclusions

The Novaquatis
research showed that the NoMix technology could represent a valuable
alternative to nutrient elimination as practised today – provided that one of
the two fundamental problems is solved: either an attractive, widely applicable
and low-cost solution needs to be found for urine transport, or stable and
cost-effective technologies need to be developed for decentralized treatment.

Water pollution due
to nutrient emissions is an increasingly serious problem worldwide, and we are
convinced that it is worth seeking solutions. However, to be competitive, innovations
require large markets. It may therefore be advisable initially to develop technologies
for fast-growing urban areas where nutrient elimination at wastewater treatment
plants is inadequate or non-existent. In this way, the NoMix technology could
rapidly and effectively help to resolve global water pollution issues. This
would require the development of attractive and economic technologies – e.g. by
Swiss companies, which increasingly operate in global markets. As solutions of
this kind also represent a realistic option for industrialized countries, implementation
of the NoMix technology in demonstration projects would make sense here, too. In
the long term, Swiss waterbodies would also benefit from the widespread
application of this system.

Problem
or opportunity? Nutrients from urine are unwelcome in waterbodies, but useful
as fertilizers (Photo Andri Bryner)

Major
potential: Urine source separation could spell big business for the sanitary industry
(Photo Keystone)